1. Field of the Invention:
This invention relates to cameras, and more particularly to cameras capable of quick and easy loading of film.
2. Description of the Related Art:
In the cameras using cartridge film, loading of the film was considerably troublesome. To improve this, in recent years, there have been made various proposals for a camera capable of simply loading film. One of the proposals of this sort is to form the back side of the camera housing with a small back lid for the cartridge chamber. Without the necessity of preliminary adjustment of the length of the tongue of film, the cartridge is set in the chamber and, upon closing the back lid, an automatic operation takes place so that, after a part of the tongue which is jutting out of the back lid has once been pulled in the interior of the camera housing, the leader of the film is fed to the takeup spool chamber, as disclosed in U.S. patent applications Ser. Nos. 026,267 filed Mar. 16, 1987 and 036,719 filed Apr. 10, 1987, both assigned to the assignee of the present invention. For the cameras of these applications however, the film in the cartridge chamber is first rewound in response to closure of the back lid to insert the jutting-out end portion of the leader of film into the interior of the camera housing. After the leader is fully stored inside the camera housing, but before it disappears in the casing of the cartridge, the motor is reversed in the direction of rotation to feed the film, toward the spool chamber. In other words, to transport the film leader in the winding-up direction, means must be provided for detecting that the leader of the film has just entered the interior of the camera housing as the rewinding of the film is performed.
As such detecting means, use has so far been made of mechanical means, or a contact switch co-operating with the film. However, this switch had drawbacks in that its operation was unstable, and that its paired contact members, when brought in contact, were apt to present a sufficient electrical conduction therebetween. Hence it became a cause of faulty operations of the camera.
Then, as a method that eliminates such drawbacks, it may be considered to use optical detecting means such as a photointerrupter instead of the above-described contact switch so that the switching operation can be carried out in non-contact fashion with respect to the film.
This method is explained in more detail below by reference to FIGS. 7 and 8. A light-emitter A and a light sensor B are positioned near the mouth of the cartridge in alignment with each other and on opposite sides of the film F. The light-emitter A starts to emit light at the same time the automatic loading operation is initiated by moving, the film F in the direction of arrow Y in FIG. 7 to insert the film leader from the outside of the camera housing into the interior of the camera housing. In the early stage, because the film F intervenes between the emitter A and the sensor B, the light issuing from the emitter A does not reach the sensor B. This implies that the leader of film F is not fully pulled in yet. As the rewinding goes on, when the free end of the film F gets off the light path, the light from the emitter A strikes the sensor B. Thus, it is determined that the intruding of the film leader into the interior of the camera housing has just been completed. Then, the direction of rotation of the motor is reversed and the film F is advanced in the winding-up direction (toward the spool chamber).
The employment of such a conventional light arrangement, however, gives rise to a new drawback as is described below. For discriminating among films at the time of development, it is usual that the film F has a plurality of penetration holes F1 bored in an area near the root of the leader. If it happens, at a time during the rewinding operation in the automatic loading mode, that one of the aforesaid holes F1 moves into the light path, the impingement of the light from the emitter A on the sensor B will be mistaken for the passage of the free end of the film F off the light path. Although the free end of the film F is, in fact, left jutting out, the motor is caused to reverse its direction of rotation so that the film leader is pushed back out of the camera housing. Thus, it becomes impossible to rely on the automatic means when loading the camera with film.